Cigarette making machine



Apnl 7, 1964 w. G. LLOYD ETAL CIGARETTE MAKING MACHINE Filed July 17, 1958 5 Sheets-Sheet l //V VE N TORS WALLACE 6. LLOYD ORV/LLE R. HARRIS 07/3 1.. UPD/KE, JR.

ATTORNEY Aprll 7, 1964 w. s. LLOYD ETAL 3,127,899

CIGARETTE MAKING MACHINE Filed July 17, 1958 5 Sheets-Sheet 2 INVENTORS WALLACE 6. LLOYD ORV/LLE R. HARRIS 0775 L. UPO/KE,JR.

ATTORNEY April 7, 1 w. G. LLOYD ETAL CIGARETTE MAKING MACHINE 5 Sheets-Sheet 3 Filed July 17, 1958 m wt 1.. NE fi 2 Emma: mQ mm L w m w w! .35 g 5 .3 \Q g n2 5 mm mk Emma 3 3w w wx. w 1 I R on 8E3. N I- Emsm I .QN QDRQ h R v& Q 2 km Iii SE28 fl 2956 MWLNNM m m m g L km m5 NNL 5 mm L 1| 6528 l S i w? M 29km? L L m k 5 Wm m QR INVENTORS ATTORNEY Apnl 7, 1964 w. G. LLOYD ETAL CIGARETTE MAKING MACHINE 5 Sheets-Sheet 4 Filed July 17, 1958 INVENTORS. WALLACE 6. LLOYD ORV/LLE R. HARRIS N 0775 L. UPD/KE, JR.

ATTORNEY 1 ployed are applicable of detection apparatus.

United States Patent 3,127,899 CIGARETTE MAKING MACHINE Wallace G. Lloyd, Richmond, and Orville R. Harris and Otis L. Updike, Jr., Charlottesville, Va, assignors to Philip Morris Incorporated, New York, N.Y., a corporation of Virginia Filed July 17, 1958, Ser. No. 749,120 39 Claims. (Cl. 13121) The present invention relates to cigarette-making machines and more particularly to control systems employed to maintain the weight of cigarettes pnoduced by such machines constant over extended periods of operation of the apparatus.

Although the control apparatus of the present invention is applicable to various types of cigarette-making machines, it is described as applied to a machine as exemplified by the machine disclosed in Molins et a1. Patent No. 2,704,079 dated March 15, 1955. In the cigarette-making machine described in the aforesaid patent, tobacco from a feed hopper is showered onto an endless moving belt or hopper tape where it forms a stream of tobacco which is passed under a larger presser roll in order to produce initial compacting of the tobacco mass. The compacted tobacco stream or rod is thereafter fed onto a travelling web of cigarette paper which is supported on a second endless belt or rod tape,

the tobacco again being compressed by a small presser roll or a shoe at the point of which it is fed onto the paper. The tobacco and paper is then formed into a rod of tobacco by the various steps of rolling, pasting, folding and heating and passes thereafter through a cutter mechanism where the rod is out into individual cigarette lengths. The cigarettes are then operated upon by two deflector devices which deflect the cigarettes into two separate rows from which an operator may take them and place them into storage bins.

Until relatively recently, the weight of the cigarettes produced by the aforesaid cigarette-making machine was controlled by the operator through the medium of a control shaft that operates upon an expanding pulley device to control the speed of a shaft driving the hopper. When a machine was initially put into operation and at periodic intervals thereafter, batches of the cigarettes were weighed and if their weight deviations were beyond predetermined tolerances, the control shaft was manipulated to an extent deemed necessary to correct for such weight deviations.

In recent years, automatic control of cigarette-making machines has been undertakemby employing devices for measuring the density of the tobacco rod prior to cutting or immediately thereafter, and controlling the aforesaid control shaft in accordance with detected weight deviations. Various density measuring techniques have been :employed; the more common of which have employed capacitive gauges and beta ray gauges. The aforesaid Molins patent employs a beta ray gauge \and it is this .type of gauge with which the present invention is concerned, although various of the techniques to be emto machines utilizing other types Beta ray density gaugesusually comprise a source of beta rays, which are high energy electrons, disposed-on one side of a moving pod of to bacoo and a Geiger-Mueller or similar gaseousdischar-ge detector .situated,.-onlthe other side of the moving rod of tobacco so that the energy detector is a function of the the wrapped tobacco rod.

produced by the beta ray .operatea motor connected to rotate the aforesaid conof the beta rays entering the density of the tobacco in The electrical output signal detector was employed to trol shaft in the proper direction to reduce deviation in the density of the rod from a desired standard weight.

3,127,899 Patented Apr. 7, 1964 Although the device described above considerably reduced the deviation in weight of cigarettes produced by the tobacco-making machines, the apparatus did not realize the full potential of this general type of control system for reasons discussed below. .In the original beta ray mechanisms, the beta ray appanatus was employed to measure the density of the wnapped rod of tobacco which is physically available only at a considerable distance from the hopper. The displacement of the measuring apparatus from the control apparatus introduces a transportation lag into the system which adversely affects the speed of response of the control apparatus. The magnitude of the transportation lag depends upon the distance between the control mechanism and the measuring mechanism, and the velocity of the stream of tobacco. In addition, the control function was applied to the main hopper drive shaft, and in consequence of inertia of the hopper mechanisms and the additional physical displacement between the hopper members controlled and the hopper tape onto which the tobacco is showered, an additional substantial delay in response to a control signal is introduced into the mechanism. It has been found in .fact that the delay in the aforesaid apparatus is of the order of magnitude of onehundred cigarettes, that is, a deviation which sheets the control mechanism does not produce an effect which is detected at the detector until after one hundred cigarette lengths have passed the detector. The lengths of cigarettes referred to here and throughout the specification, relate to the lengths of regular size cigarettes customarily having a length of approximately 70 millimeters.v Limitations on the rapidity of control that could be obtained by the original Molins device were further compounded by the fact that a relatively long Geiger-Mueller or related gaseous discharge type tube was employed for sensing or detecting the beta ray emanations. Specifically, the low density of the detection material in a Geiger- Muel-ler tube requires that a relatively long length of the tube be activated by the beta rays in order to produce a signal of sufiicient intensity to be detectable in the presence of considerable background noise produced by such things as tobacco dust, paper dust and related phenomena.

An additional problem notsolved by the original apparatus resulted from variations in thickness of the rod tape with time, which has been found to amount to as much as 20% of the weight of the cigarette overextended periods of'use of the machine. Obviously, some correction must be provided for such variations and also variations in operating conditions of the detector itself in an environment which varies in temperature, moisture and related physical aspects. Also, variations in the intensity of the beta ray source introduced inaccuracies into the machine and transverse vibnation of the round rod produced a variation in the thickness of the unit being measured and, therefore, introduced considerable flutter into the circuit.

Improvements in the original machine were presented in Molins et al. Patent No. 2,737,186, dated March 6, 1956, wherein in one embodiment of the invention, the large pressure roll was removed so that the beta ray source and detector could be placed immediately adjacent the hopper in order to reduce transportation lag. Additional improvement was effected by compensating for variations in thickness of the belt by utilizing a standard source and detector which measured among other things the thickness of the belt so that the elfects of belt wear were reduced. Although this system eliminates some of the difficulties with the control system of theoriginal device, it introduces new problems in that it attempts to form a uniform rod of tobacco in-a machine from which the large presser roll has been removed. Also, the apparatus does not eliminate the inertia of or the transportation lag in the hopper mechanism itself. In consequence, the overall inertia of the system was not appreciably reduced. Further, due to physical limitations of size of the detector and space available on the machine, the balance detector is removed a considerable distance from the weight measuring detector and, therefore, does not eliminate the effects of local variations in the belt. Also, the utilization of two sources of beta rays and detectors again does not eliminate the effects due to variations between the two sources of beta rays.

The necessity for removing the large presser roll when it is desired to place the beta ray source detector immediately adjacent the hopper is a result of the extreme compactness of the original cigarette-making machine of interest in this application, which does not provide much unused space of a size required to mount beta ray sources and detectors of the type utilized by the Molins et al. machine. In an effort to eliminate some of the transportation lag inherent in the device of Patent No. 2,737,186, dated March 6, 1956, a completely new feed system is disclosed in Molins et al. Patent No. 2,800,131, dated July 23, 1957. In this patent, basically, the tobacco is showered onto an endless conveyor which feeds the tobacco through an intermediary feed mechanism onto a stretchable belt. The length of the belt is increased or decreased depending upon whether the instantaneous weight of tobacco, as determined by a source and detector mechanism immediately adjacent the feed to the belt, is heavy or light. The tobacco coming off of the stretchable endless belt is fed between a rigid inclined plate and a relatively rigid endless belt that compresses the tobacco and feeds it onto a web of cigarette paper conveyed by a conventional rod tape Where a second ionization gauge, intended to control long term variations of the machine, is located.

The system described above provides a completely new feed mechanism for the tobacco machine and utilizes two distinct measuring and control mechanisms, one for controlling short term variations and one for controlling long term variations in the weight of the tobacco in the stream. Although the apparatus of this latter patent does overcome many of the difficulties of the devices of the two aforesaid patents, the apparatus does not eliminate the effect of variations in belt thicknesses between two distinct belts, it does not eliminate the effects of variations between two distinct beta ray sources and foremost it requires expensive modifications of existing machines in order to install the apparatus. It will be noted also that although the one source and detector mechanism affords control of relatively short term variations of the weight of the tobacco stream, there is a greater transportation lag between the second ionization chamber and the hopper than in the previous machines and therefore the effects of long term variations are more dificult to overcome.

The variations of the Weight of tobacco from the hop per result from two distinct effects. One effect produces long time variations and results from gradual changes in the total quantity of tobacco fed from the hopper. The other effect produces short time or point-to-point variations in the quantity of tobacco along the length of the rod and results from transient variations in the quantity of tobacco being supplied at a location along the width of the hopper. In the latter Molins machine, the short time circuit may correct, within limits determined by the length of the detector, for variations in weight due to transient variations in the quantity tof tobacco supplied, but it cannot correct long time variations resulting from changes in speed of the hopper or changes in moisture content or temperature of the tobacco. These latter factors must be controlled by the second and more conventional ionization detector employed in this patent and the transportation lag again becomes a considerable factor in this portion of the control function.

It is an object of the present invention to incorporate into a cigarette-making machine of the type with which the present invention is concerned and with a minimum of modification of the machine, a scintillation detector control mechanism which corrects irregularities in the amount of tobacco supplied to the machine on both a short time and/or a long time basis ranging from a quarter cigarette length to a thousand cigarette length.

It is another object of the present invention to provide a radiation detector of such a short length that the amount of tobacco fed to the machine may be controlled over quarter cigarette lengths.

It is another object of the present invention to provide a cigarette-making machine having a radiation detector mechanism for measuring the weight of tobacco supplied to the machine and a tobacco feed arrangement permitting variation of the amount of tobacco fed thereto over quarter cigarette lengths.

It is yet another object of the present invention to provide a radiation source and detector arrangement which permits elimination of the effects of variation in the rate of radiation of sub-atomic particles from the source from the measuring system and which substantially reduces the effects of variation in the thickness of the endless belts utilized to transport the tobacco.

It is another object of the present invention to provide a cigarette-making machine and a radiation control arrangement therefor wherein the radiation source and detector may be located relatively closely adjacent to a main source of tobacco without requiring material alteration of the structure or the operation of the cigarettemaking machine.

It is still another object of the present invention to provide a radiation source and detector for measuring the weight of tobacco supplied from a feed mechanism to a cigarette rod making machine and to utilize the signals produced by the radiation detector for controlling one or more closed loop control mechanisms and/ or open loop control units.

It is another object of the present invention to provide a control mechanism for a hopper fed tobacco making machine provided with a control mechanism having a sufficiently short response time to compensate for transient variations in the quantity of tobacco along the length of the rod.

Yet another object of the present invention is to provide a cigarette-making machine employing a tobacco density measuring and control unit for controlling the rate of feed of tobacco from a main tobacco feed mechanism and from one or more low inertia auxiliary tobacco feed mechanisms.

In accordance with the present invention there is provided a cigarette-making machine of the general type illustrated in Molins et al. Patent No. 2,704,079 utilizing a hopper mechanism for showering tobacco onto an endless belt or hopper tape. The hopper tape conveys the tobacco under a pressure roll, so that the tobacco is initially formed into a compacted mass and thereafter conveys the tobacco onto the cigarette paper which overlies the paper and tobacco through the remainder of the mechanism which forms the paper and tobacco into a rod and thereafter cuts the rod into cigarettes and deflects the cigarettes into two separate streams. The machine is normally provided with a small pressure shoe overlying a rotating pulley or idler wheel over which the tobacco paper and rod tape pass at the point that the tobacco is applied thereto. In the present invention, the pressure shoe is modified to support a radiation detector and an idler roller, hereinafter referred to as the tube roller, disposed immediately below the pressure shoe, and over which the paper and endless tape pass at the point the tobacco is placed thereon, and is modified to contain therein a source of radiation and preferably a source of beta rays. Dispressed rod In consequence of the arrangement or disposition of thesource of radiation in the aforesaid roller and the utilization of this source to activate both a measuring detector and a reference weight and compensating detector, the effects of variations in the instantaneous intensity or quantity of emanations from nated from the output signals produced by the measuring apparatus. Further, since in the conventional machines the roller, which has been modified in accordance with the present invention to include the source, is approximately two inches in diameter, the lengths of the belt which passes between the source of radiation and the measuring detector on the one hand and the source of radiation and the compensating detector on the other are displaced only by about three inches and in consequence all but the short term variations in the thickness of the belt are removed from the measuring circuit. A piece of metal such as aluminum is placed between the compensating detector and the belt in line with the source of radiation so as to provide.

a standard reference weight against which the weight of the tobacco may be measured. In consequence the latter detector provides a signal that is employed as both a standard reference signal and compensation signal to reduce the effects of variations in various environmental conditions of the apparatus.

Continuing with the description of the apparatus of the present invention, the usual ionization tubes employed in such machines are replaced by scintillation detectors so that relatively short lengths of tobacco may be measured. The ionization tube, since it utilizes a gaseous detection medium, is required to be a relatively large volume device due to the low density of the detection material so that it may have adequately high detection efiiciency. The scintillation crystal is normally employed in scintillation counters of this type, and in the present invention stilbene or anthracin may be employed. Both of these materials are quite dense and in consequence are far more sensitive in smaller volumes than the gaseous medium employed in ionization tubes. Therefore, a smaller solid angle need be subtended to produce the same effect as is produced by measurement of a larger solid angle with an ionization tube. In conseqence a shorter length of the tobacco is measured and control may be effected over shorter lengths of the cigarette. A mathematical analysis of the problems encountered in measuring changes over predetermined lengths of the cigarette rod and of the relationship of the length and shape of the source results in a specific formula which in accordance with the invention relates the optimum length of the source to the speed of movement of the cigarette rod and further provides a shape of detector which increases response of the detector to weight variations occurring at various rates. Specifically, adetector shape is chosen which provides for a gradual entry of the rod into the detector region and gradual retreat of the rod from the detector region; this effect being obtained by utilizing a detector having rounded edges intersecting the rod.

The entire source and detector arrangement occupies a relatively small space and may be applied to the machine by making relatively minor modifications therein. Specifically, the aforesaid roller is modified to contain the source and the pressure shoe is modified to support the measuring detector. The pressure shoe extends from the large presser roll to a location downstream where the tobacco rod is formed. The shoe is mounted between guide members which together with the shoe and the supports for the endles tapes maintain the tobacco in a comhaving a rectangular cross section.

The tube roller mechanism in which the radiation source is mounted constitutes a stationary central hub or shaft having a central diametric aperture passing therethrough, the aperture constituting a vertical passage through the the source are effectively elimi-' plunger or piston roller shaft. The apertureis suitablybored to provide collimators for the beta-rays issued from the source in both directions. The source is mounted in an axially-slidable which when the apparatus is to be employed is aligned with the diametrical aperture so that the radioactive emanations proceed to the measuring and compensating detectors. When the apparatus is deenergized, a spring, whose effect is overcome by an electromagnet when the apparatus is energized, pushes the beta ray sourceaxially of the roller shaft and disposes the source in a solid portion thereof so asto render the source safe; that is, so as to prevent any appreciable amount of radioactive emanations from being emitted-into the surrounding region.

Disposed about the shaft of the tube roller is an outer, substantially tubular member mounted on ball bearings for rotation about the axis of the roller shaft and therefore constitutes the rotating portion of the tube roller assembly. The tubular-member is provided with a circumferential window of a predetermined thickness aligned with the collimator apertures formed in the roller shaft. The thickness of these windows are'appropriately chosen with regard to the intensity of the beta ray'source such that the energy of the beta rays passing through the mass of tobacco is such as to produce an optimum variation in output signal with variations in density and therefore weight of the tobacco. More specifically, it is a well-known phenomenon of the field of radiation that the change in energy of beta rays with a change in density of the material being measured follows a predetermined curve in accordance with the initial energy of the beta rays. If the initial energy of the rays is of the proper value, the variation in energy of the rays reaching the detector is greatest for a given change in density of the material. Therefore, the thickness of the windowsin the rollerof the roller assembly is correlated to the strength of the beta ray source so as to provide for maximum two guide signal change with density changeof'rthe: tobacco.

As previously indicated, the tobacco is passed between. members which force the tobacco to remain in a square cross-section and the material is chosen such that the beta rays are reflected from the side guides back through the tobacco so as to increase the quantity of beta rays reaching the scintillation crystal and therefore increases the magnitude of the signal produced by the measuring detector. Further, the multiple reflections of the beta rays through the mass from the guide wallsprovides for better coverage of the cross-section of the tobacco since it measures all portions of the crosssection of the mass. A distinct advantage is obtained in consequence of the source and the compensating and measuring detectors being aligned. Back-scattering from the tobacco which normally would subtract from the magnitude of the signal increases the magnitudeof the signals in the present invention. The back-scattered particles proceed downthrough the aperture in the roller shaft and to the compensating detector. In the present invention the outputs of the two detectors are subtracted from one another by causing the output of one of the detectors to appear as a positive signal and causing the output of the other detector to appear as a negative signal and then adding the two signals. Since the amount of back-scattering from the tobacco is an indication of its density, the back-scattered emanations, subtracted from the signal produced by the measuring device, are added to the signal produced by the compensating device. Thus there is a definite increase in signal intensity as a result of this back-scattering and the sensitivity of the entire instrument is greatly increased.

Proceeding now with the description of the control apparatus of the tobacco-making machine of the present invention, the control signal produced by the radiation detection and measuring circuit is utilized to control the hopper speed so as to compensate for long term variations in the weight of the mass of tobacco being fed to the cigarette-making machine. Regulation of the hopper speed provides a control over a range of one-hundred to one-thousand cigarette lengths and is the control disclosed in the aforesaid Molins patent. The control may be applied simultaneously or alternatively to control the speed of the pin-roller of the hopper mechanism so as to provide control of the cigarettes over thirty cigarette lengths. The effect and advantage of controlling the pin roller in conjunction with the main drum as opposed to control of the main drum alone are discussed in US. Patent No. 2,948,281, assigned to the assignee of the present invention.

A further control which may be provided in accordance with the present invention is control of the effective length of the hopper along the hopper tape. Control of the speed of the hopper mechanism whether it be of the main drum or of the pin roller produces a gradual change in the total weight of the tobacco along the rod, from the original weight which is to be corrected to the final weight which is called for by the detector. This may be pointed out by considering the effect of the change in speed of the hopper mechanism upon the total quantity of tobacco showered on various locations along the tape at the time the change in hopper mechanism speed takes place. The total quantity of tobacco adjacent the downstream end of the hopper is substantially unaffected by the change in speed of the hopper mechanism since substantially all of the tobacco has been accumulated at this point. On the other hand the total quantity of tobacco eventually accumulated at a point which is intermediate the ends of the hopper when the change takes place has its weight increased or decreased as the case may be by 50% of the total change since during the last half of its run through the hopper it is receiving tobacco at the new rate. The total quantity of tobacco accumulated at a portion of the hopper tape located at the upstream end of the hopper when the change occurs is at the new weight since this section of the hopper tape receives tobacco for the full length of the hopper opening in the direction of the tape travel. However, the weight of the tobacco may be affected by a movable plate or a defiectable vane and in addition may be aflected by an airblast or other suitable methods for removing a portion of the tobacco that is being showered on the hopper, plate, adjacent its downstream end.

In a further specific feature of the present invention one or more auxiliary sources of tobacco are provided and are located closer to the radiation source and detector than the main hopper. The auxiliary sources have a considerably lower inertia than the main hopper in response to a control signal which may be applied thereto except for the hopper width control. In a specific example, not intended to exclude other equally appropriate ratios or proportions, approximately 90% of the tobacco required may be supplied by the hopper and the remaining of the tobacco may be supplied from one or more auxiliary hoppers having relatively low insertias. A first of these sources may be located between the main hopper and the large presser roll so that this source would be only approximately three cigarette lengths away from the detector. Such an arrangement provides a relatively short term control over the apparatus, particularly if the hopper mechanism has substantially no mechanical inertia.

A low inertia hopper which may be employed to provide a nominal 10% of the tobacco required includes a vane-type deflector. The deflector may be rapidly moved by an electromagnet so as to extend a greater or lesser distance into a stream of tobacco being showered onto the hopper tape so as to deflect greater or lesser quantities of the tobacco away from the tape. Since the only inertia encountered in such a system is the inertia of the deflecting vane, which is obviously quite small, the mechanical inertia of the system may be neglected for purposes of analysis and will have substantially no effect upon the rate of operation of the machine. Since this auxiliary source of tobacco is located only three cigarette lengths away from the detector and its inertia may be neglected for all practical purposes, the control provided thereby is over a three cigarette length. By the utilization of still more auxiliary sources the transportation lag between the detection of an error in density and a compensating control for the error may be still further reduced. Specifically, a further low-inertia auxiliary source may be placed down stream from the detector and provides an open loop substantially instantaneous control for the apparatus. The latter source compensates for variations in the density of the tobacco limited only by the length of the scintillation crystal employed in the detector. Assuming that the length of this crystal is of the order of magnitude of a quarter length of a cigarette, then the apparatus of the present invention may control variations in density of tobacco in the rod over lengths of the order of one-quarter cigarette. It will be noted that this type of control is an open loop control and therefore if desired, a delay may be provided between the detector and the latter auxiliary source so that the source varies the amount of tobacco to the rod at the precise moment that the tobacco which produces the error signal is disposed under the auxiliary source. In consequence, of the utilization of a main hopper source which may be controlled at three dilierent points and of one or more auxiliary sources which normally supply a predetermined portion of the tobacco, a wide range of controls over a large number of cigarette lengths may be effected and specifically in accordance with this invention control may be achieved on lengths varying from one quarter cigarette lengths up to one-thousand cigarette lengths.

It is another object of the present invention to provide a cigarette-making machine having a main source of tobacco and at least one relatively low inertia auxiliary source of tobacco, the rate of feed of both of which is controlled by means of a density-determining, beta ray source and detector mechanism.

It is another object of the present invention to provide a beta ray source and detector mechanism wherein the source is located in a roller of the machine and the measuring detector and the compensating and reference detector are diametrically aligned on opposite sides of the roller so as to minimize displacement between the detectors.

It is another object of the present invention to provide a cigarette-making machine wherein the normally provided small pressure roll is removed and its function is performed by the beta ray detector housing substituted therefor.

It is another object of the present invention to provide a beta ray source holder for utilization in rod-type cigarette-making machines wherein the holder constitutes a roller of the machine fabricated so that during periods when the machine is not being utilized, the beta ray source may be disposed in a position such that no high energy emanations from the source can reach the exterior of the roller.

It is still another object of the present invention to provide a cigarette-making machine having a radiation actuated control mechanism in which one of one or more auxiliary sources of tobacco are disposed immediately adjacent to the radiation source and the detector.

It is yet another object of the present invention to provide a beta ray source and detection mechanism which utilizes beta rays having an initial energy such that the energy of the rays reaching the detector undergoes a maximum variation in energy with variation in density of material and to utilize detectors employing dense scintillation crystals so as to minimize the length of the crystal required with respect to the direction of travel of the mass of tobacco to be measured.

It is another object of the present invention to provide a cigarette-making machine of the rod-type and a scintillation source and detector arrangement for measuring the density of the mass of tobacco supplied to the machine prior to formation of the wrapped tube and specifically to measure a rectangular cross-section of the tobacco rod so as to substantially reduce the effect resulting from transverse vibration of the moving mass and further to utilize metal side members for side guides for the mass, which side guides reflect the beta rays and therefore eifect an investigation of a greater portion of the volume of the rod than would otherwise be possible.

It is another object of the present invention to provide a cigarette-making machine of the rod-type and a scintillation source and detector arrangement for measuring the density of the mass of tobacco supplied to the machine and further to eifect the measurement of the tobacco rod density before it is Wrapped so that instantaneous or very short term variations can be corrected prior to wrapping by means of an open loop control mechanism.

It is still another object of the present invention to provide a cigarette-making machine with a hopper mechanism that may be controlled at three points to provide control on a one-hundred to one-thousand cigarette basis, on a twenty-five to one-hundred cigarette basis, and on a fifteen to twenty-five cigarette basis and further to provide a first auxiliary hopper for controlling the mass on a basis of three to ten cigarettes and finally to provide a second auxiliary hopper disposed downstream of the measuring and detection apparatus for controlling the rod on the basis of a one-quarter cigarette length to two cigarette lengths.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a side elevation of a continuous rod cigarette-making machine showing the location of the radiation source and detector mechanism and the auxiliary tobacco sources;

FIGURE 2 is a detailed cross-sectional view, taken along line 2-2 of FIGURE 4, of the source roller mechanism and the detector mechanisms utilized in the machine of the present invention;

FIGURE 3 is a detailed view of the mounting arrangement for the radio active source container in the source holder;

FIGURE 4 is a side view in elevation of the mounting for the roller containing the beta ray source and for the device measuring the density of the tobacco rod;

FIGURE 5 is a detailed view in elevation of an auxiliary hopper which may be utilized with the apparatus of the present invention;

FIGURE 6 is a graph illustration of the relationship between the change in beta ray energy per change in density of a material plotted against initial beta-ray energy;

FIGURE 7 is a flow diagram of the control apparatus of the present invention;

FIGURE 8 is a partial Wiring and partial schematic diagram of the electrical control apparatus of the mechanism of the present invention;

FIGURE 9 is a front elevation view of the variable width main hopper of the invention;

FIGURE 10 is a view taken along line 1010 of FIG- URE 9;

FIGURE 11 is a graph illustrating the amplitude of signals developed by the detector in accordance with changes of weight of the tobacco rod as a function of the frequency of Weight variations; and

FIGURE 12 is a partial transverse section in elevation of the hopper showing a generally conventional arrangement of tobacco feed elements.

Referring specifically to FIGURE 1 of the accompanying drawings there is illustrated a rod-type automatic cigarette-making machine of conventional design constituting a main feed hopper 1 for showering tobacco onto a moving endless belt or hopper tape 2 disposed in a U- shaped channel member 3. The tobacco showered onto the hopper tape 2 is conveyed between side guide members 4, only one of which is illustrated in the accompanying drawings, and under a large presser roll 6 which compresses the tobacco into a rod having a relatively square or rectangular cross-section. A web 7 of cigarette-paper is taken from a paper feed drum 3, passed through a printing mechanism 9 and eventually proceeds via various rollers over a tube tape roller 11, wherein the paper is brought into overlying relationship with a second endless belt or tube tape 12 and is thereafter conveyed through a cigarette r-od forming and cutting sections of the machine. The compressed tobacco on the belt 2 is delivered onto the web of cigarette paper '7 adjacent the roller 11', and the tape 12 conveys the tobacco and the paper through a wrapper 13, a paster 14, a heater 16, a cutter 17 and deflector blades 18 and "19 which deflect the cut cigarette into two channels disposed'in front of the machine operator.

In the conventional cigarette-making machine of the rod type as illustrated in the aforesaid Molins Patent No. 2,704,079 and also to limited extent in the machine of the present invention, in order to vary the rate at which tobacco is showered onto the tape 2 by the hopper 1, there is provided a control shaft 21 which through a suitable mechanism to be described determines the rate of rotation of a drive shaft 22 which supplies rotary power to the various elements of the hopper 1. Mechanical power is supplied to the machine via a shaft 23 which drives belt 25 through a variable speed cone-type or expanding pulleytype transmission 24. The rate of rotation of the belt 25 is determined by the angular position of the shaft 21 whose position is controlled by a reversible drive motor 26. The motor 26 constitutes one of the members responsive to signals indicating deviation of the weight of the tobacco from a desired value. The variable speed clutch 24 drives a wheel 27 secured to one end of the hopper drive shaft 22.

Thus far the apparatus of the present invention is substantially identical with that disclosed in the aforesaid Molins Patent 2,704,079 with the exception that the small presser roll has been removed. Proceeding now to the novel features of the apparatus of the present invention, there is provided in the roller 11 a source of radio-active emanations, preferably beta-rays. Disposed immediately above the roller is a measuring detector 28 and disposed immediately below the roller 11 is a reference and standard detector 29 both for measuring the intensity of the beta rays impinging thereupon after proceeding through various portions of the mechanism. In FIGURE 2 of the accompanying drawings, which is a detailed cross-sectional view of the beta ray source and beta ray detector mechanisms, the tube tape roller 11 comprises a stationary roller shaft and collimator 31 having a cylindrical axial channel 32 extending from one end thereof and terminating in a solid end wall 33. The cylindrical channel 32 is intersected substantially at right angles by a pair of transverse, diametrically-opposed, apertures 34-. The apertures 34 have the form of truncated cones with their largest diameters adjacent the outer circumference of the shaft 31. The taper of the conical apertures 34 determine the solid angle to which the emanations from the radioactive source are confined.

The shaft 31 is supported between a pair of side guides 36 and 37 which are secured to the machine in a manner to be described subsequently. Rotatably mounted on a pair of axially displaced ball bearing assemblies 38 and 39 is a tubular roller 41 over which the tube tape 12 and the paper web 7 are guided. The tubular roller 41 is crowned as at 42 so as to prevent excess transverse movement of the tape 12. The tubular roller 41 is internally recessed so as to provide a thin walled portion or circumferential window 43 radially aligned with the aperture 34. The thickness of the window 43 is precisely i ll determined in accordance with the energy of the emanations of the radio-active source for reasons to become apparent subsequently. Disposed within the cylindrical aperture 32 in the shaft 31 is a piston or plunger 44 that is spring-biased to the right as viewed in FIGURE 2 by means of a compression spring 46. The spring 46 is disposed about a shaft 47 secured to the left-end of the plunger 44. The piston 44 is slidably movable in the cylindrical aperture 32 and is retained in the position illustrated in FIGURE 2 by means of an electromagnet 4% disposed within a housing 49 secured to the guide 36 by suitable means such as bolts 5th. The housing does not appear in FIGURE 1 and was eliminated therefrom in order to clarify the drawing, since if the housing had been included in the drawing the roller 11 would have been obscured.

The piston 44 is provided with a transverse aperture 56 located in the center of the piston 44 and having a diameter approximately equal to the smallest diameter of the apertures 34. A beta-ray source 54- is adapted to be disposed in the aperture 59 and to this end (reference is now made specifically to FIGURE 3 of the accompanying drawings) one-half of the surface of the piston defining the aperture 54 is threaded to receive a threaded source container 5'1. The source container 51 constitutes a hollow cylindrical and externally threaded sleeve having adjacent the end which is located centrally of the aperture Sll a portion of increased diameter defining a shoulder 53 against which is seated a disc 55 of material for emitting sub-atomic particles such as betarays. Various sources of beta-rays are well-known in the art and as an example may constitute a twenty millicurie, strontiumyttrium 90 source in a silicate binder, the conventional symbol for the source being Sr-Y90. The disc 55 is supported between two relatively thin Monel discs 56 and 5'7 to provide proper support for the disc and a leak-proof seal.

In consequence of the above arrangement a beta-ray source of predetermined intensity or energy level as measured in millicuries is disposed along the center line, both longitudinally and transversely, of the roller arrangement 11 and is, when the machine is in operation, aligned with the collimating aperture 34 in the roller shaft and collimator 31. When the machine is in use, beta-rays are emitted through the window 43 in the tubular roller 41 and proceed to the two radiation detectors 28 and 2?. As previously indicated, a compression spring 46 biases the plunger 44 toward its right hand position so that if nothing else were acting upon the plunger 4-4 it would be disposed with its central portion 45, removed from the collimating aperture 34 and effectively isolated from the surrounding atmosphere, when the machine is out of use. When the machine is in use, the electromagnet 4S disposed in the housing 4% and connected to the shaft 47 is energized and moves the plunger 44 against the compression spring 46 so that the source 54 is aligned with the collimating aperture 34 and the measuring apparatus is rendered active. The electromagnet 48 is preferably connected into the main electrical circuit to the drive motor of the machine. FIG. 2 shows a main switch S and electrical connections 43a to the solenoid 48 whereby the latter is energized when the main switch is closed. A stop may be incorporated in the magnet 48 or connected to the shaft 47 to align the source 54 accurately with the aperture 34. In FIG. 2 the stop is shown as an adjustable set screw 47a threaded through the end wall of housing 49 adapted to be engaged by the end of shaft 47 when the magnet 48 is energized. The set screw 47a may have a lock nut 47 b.

Disposed immediately above the roller 11 and spaced therefrom by a relatively small distance of the order of magnitude of twenty-live thousandths of an inch is a tobacco guide 58 constituting two side guides 59 and 61 having generally rectangular cross-sections. The rectangular guide members 59 and 61 define a rectangular crosssection therebetween for the tobacco to pass through and are vertically recessed (reference now being had to FIG- URE 4) to provide a generally rectangular recess 62 in the upper portion of the wall of each of the guides 59 and 61. Disposed between the side guides 59 and 61 and secured thereto as by bolts 63 and 64 is a longitudinallyextending shoe 66 including a hollow cylindrical sleeve 67 extending between and disposed in the rectangular grooves 62 in the guides 59 and 61. The hollow cylindrical sleeve 67 is axially aligned with the collimating aperture 34 in the roller 11 and is clamped as by bolts, about a lower hollow cylindrical end member 68 of the scintillation detector 28.

The lower surface of the shoe 66 defines the upper surface of the rectangular guide-way for the tobacco, constituted by the tape 12 and paper web 7 on the bottom, the guides'59 and 61 on the side and the shoe 66 on the top. The shoe 66 extends to the pressure roll 6 and its upstream edge is arcuate, having approximately the same radius of curvature as the pressure roller 6 and therefore substantially mating with the downstream edge of the pressure roller. In consequence, tobacco passing under the pressure roller and emerging on the downstream side thereof passes under the shoe 66 and subsequently between the roller 11 and the measurement detector 28 while being maintained under compression. The removal of the small pressure roller on the standard machine with which the present invention is concerned has little or no effect on the final product produced thereby, since its function is performed by the members described above. The shoe 66 is suitably supported by a support member anchored to the machine at one end and seated in a channel 71 and an elongated aperture '72 formed in the upper portion of the shoe 66. Suitable means may be provided for securing the support to the shoe and retaining it in the channel and aperture.

As previously indicated, the lower portion of the scintillation detector 28 constitutes a vertical cylindrical end member 68 supported in the ring 6-7 of the shoe 66. The vertical end member 68 is provided with a circumferential horizontal flange 73 clamped to a main housing 74 of the detector 218 by means of an end nut 76 threaded onto the body 74 and having an inwardly directel horizontal flange 77 engaging the lower surface of the circumferential flange 73. The lower end of the end member 68 is closed by a window '78 of a predetermined opacity to beta rays as determined by the energy of the source 54. Mounted immediately above the Window 78 is a scintillation crystal 79, which may be anthracin or stilbene or other suitable material, secured to the lower end of a cylindrical Lucite body 81, having a T-shaped crosssection. The crystal '79 responds to beta rays to produce flashes of light having an intensity determined by the intensity of the beta rays. The light flashes produced in the crystal 79 are conducted through the Lucite body 81 supported on the horizontal flange 73 of the member 68, to a photo-multiplier tube 82 suitably supported in the casing 74. A hollow cylindrical insulating sleeve 33 lined with a metallic cylindrical sleeve 85 is tightly fitted into casing 74. Thus sleeve 85 is insulated from casing '74- so that while the latter is maintained at ground potential, sleeve 85 can be maintained at a high negative potential to increase the photo-electric collection efficiency of photo-multiplier 82. A suitable optical coupling fluid of high viscosity is disposed in a space 84 between the lower end of the photo-multiplier tube 82 and the upper end of the Lucite member 31 so as to increase the light conduction between these two members and conserve as much or" the signal as possible. The body '74 in which the photo-multiplier tube 82 is mounted, is additionally supported by means of a U-shaped clamp 86 disposed about the body '74 and secured to an upright member on the machine.

The reference and compensating detector 29 is substantially identical with the detector 28 and the refer- 13 once numerals applied to the structure are the same as those applied to detector 23 with primes applied thereto.

A U-shaped member 87 (see FIG. 2) may be provided about the body of the detector assembly 29 to further support the apparatus. Disposed between the roller 11 and the detector 29 is a sheet 3 8 of suitable metal such as aluminum having an absorption characteristic that is substantially identical with the absorption characteristic of the density of tobacco to maintain in the space between the roller 11 and the detector 28. Thus, the sheet of metal 88 constitutes a standard or reference density against which the density of the tobacco may be compared.

The foregoing describes the general features of the physical embodiment of the detector means. The details and characteristics of the scintillation detectors and associated photo-multipliers need not be elaborated upon herein since they are commercially available and well known to those skilled in the art. The patents to Wouters 2,554,933, dated May 29, 1 951 and 2,594,703, dated April 29, 1952 each disclose circuits embodying scintillation crystals and photo-multipliers. Reference may also be had to the article Regulation of the Individual Dynode Voltages for Photomultiplier Tubes by O. R. Harris and B. dE. Flagge appearing in the IRE Transactions on Nuclear Science at pages 3 to 11 of the March 1957 issue.

Referring now to the various types of controls which may be affected in accordance with the present invention, the speed of the hopper apparatus may be varied by varying the rate of rotation of the drive shaft 22, or the speed of the pin roller may be varied by the drive shaft 22 and the remainder of the mechanism slaved to the speed of the pin roller all in accordance with the aforesaid patent to De Voto et al. A further hopper con-trol which may be provided is that relating to varying the effective width of the hopper along the hopper tape. Referring specifically to FIGURES 9 and 10 of the accompanying drawing, the hopper 1 includes a chute 99 which directs the tobacco from the main section of the hopper onto the hopper tape. A portion of the forward wall 99 adjacent the downstream end of the hopper '1 is provided with an elongated horizontal slot 190 extending over a predetermined width of the hopper. A slidable flat plate 165 extends from in front of the front wall 99, through the slot 190' and into engagement with the rear wall of the section 99 of the hopper 1, being disposed at an angle of approximately 0 with the horizontal, this being the fall angle of tobacco. The plate :105 is adapted to be moved along the length of the slot 190' by means of a suitable drive mechanism 110 which may constitute a variable position relay or an electrical motor drive. The plate 195 extends sufiiciently forward of the front wall 99 of hopper 1 to carry whatever tobacco that falls thereon to a position forward of the hopper tape guide so that the tobacco may be dropped upon a suitable conveyor mechanism for removal. The lower edge of the plate 105 may be suitably supported as by resting on a groove guide located between the tape guide and the conveyor.

That portion of the tobacco provided by the hopper 1 which falls on the plate 105 slides down the plate, out through the slot 190 and therefore is prevented from showering onto the hopper tape. The quantity of tobacco which is deflected from the hopper tape is determined by the length of the plate 105 inserted in the slot 190 and therefore the depth penetration of the plate 105 into the slot 10%} determines the quantity of tobacco accumulated on the hopper tape. The end of the hopper 1 is located approximately four cigarette lengths from the beta-ray source 54 and detector 28, and if it is assumed that the center position of the plate 195 is with its upstream edge extending approximately one cigarette length into the slot 100 then the average transportation lag between the control effected by the mechanism of FIGURES 9 and 10 and the source and detector arrangement is five cigarette lengths. If the weight of the cigarette is to be increased and therefore the plate 195 must be retracted, transportation lag is reduced whereas if the weight of the tobacco is to be decreased and the plate 105 must be inesrted further into the slot the transportation lag is greater than five cigarettes. However, the average transportation lag is equivalent to five cigarette lengths and due to the relatively light weight of the plate 195, which may be fabricated from aluminum, the inertia of the system is quite low and the effective inertia of the system may be considered that resulting from transportation lag.

Returning again to the apparatus illustrated in FIG- URE 1, the hopper 1 is intended to provide the majority ofthe tobacco for the cigarette-making operation, but additional sources of tobacco are provided in accordance with the present invention and are adapted to supply a predetermined portion of the tobacco, as required by a particular installation, and for instance, from five to fifteen percent of the tobacco required. One of these sources, a tobacco source 91 is arranged to shower tobacco onto the tape 2 between the hopper 1 and the presser roll 6. The machine may utilize additional auxiliary feed apparatus and specifically may employ a second feed apparatus 92, of approximately the same design as the apparatus 91, adapted to shower tobacco onto the tape 12 downstream from the roller 11 and the detectors 28 and 29. If a hopper is employed downstream from the sourcedetector, the forward edge of the tongue of the rod forming apparatus must be recessed about to permit tobacco to enter the stream. As indicated in FIG. 4 the auxiliary tobacco feed supply 91 has a conduit connection 91 into the shoe 66 which rides over the top of the tobacco stream, and auxiliary feed 92 has a conduit con nection- 92 into the top of the wrapper folder 13 adjacent the right end where the tobacco wrapper tube is still open at the top and capable of receiving a small stream of tobacco where dictated by the automatic controls to be described more fully hereinafter.

Referring now specifically to FIGURE 5 of the accompanying drawings, which illustrates the various elements of the auxiliary feeds arranged transversely of the path of movement of the tobacco stream, the feed mechanisms 91 and 92 are generally similar and each constitutes an upper mechanism for providing a shower of tobacco, generally designated by the numeral 96, between a side wall 93 and a central portion 94 of the mechanisms 91-- 92. Disposed in the path of the shower of tobacco 96 internally of the machine is a movable vane 97 secured to a rotatable shaft 98 which upon being rotated clockwise or counter-clockwise, extends the vane 97 to a greater or lesser extent, respectively, into the path of shower of tobacco 96. The tobacco deflected from the downward stream by the vane 97 falls upon an endless conveyor 99 moving in the direction of the arrow 101 and is conveyed to a location adjacent a wall 192 remote from wall 93. Suitable means such as an air blast or suction may be provided for removing the tobacco from the endless conveyor 99 and returning it to the upper portion 95 of the feed mechanism where the tobacco may again be fed into the shower of tobacco 96.

As previously indicated the source 91 is to provide a predetermined proportion of tobacco on the main stream and for purposes of illustration may be assumed to provide a nominal 10% of the total stream. The correction which may be effected by control of the source 91 is dependent upon the percent variation in the nominal percentage supplied thereby and may amount to 5% so that the total proportion provided by source 91 may vary from five to fifteen percent. The source 92 on the other hand may provide only one to two percent of the tobacco in the stream. With regard to both of the sources 91 and 92, they may be operated at high rates of feed so that the instantaneous feed capacity may be small and therefore they may be of small size. This is advantageous in maintaining the physical dimensions of the vanes 97 smallso that they have an almost instantaneous response as compared with the rate of travel of the tobacco stream. Since substantially no inertia effect is introduced into the control function by the apparatus 91 and it is located relatively close to the source 54, the lag in control as measured by cigarette lengths, is very short and may amount to three cigarette lengths. In the case of the source 92 there is no transportation lag since it is located downstream from the detector 28 and response is limited only by the length of the scintillation crystal.

Proceeding now to a description of the operation of the apparatus of the present invention, tobacco as in the conventional machine previously discussed, is rained onto the tape 2, is pressed by the presser roller 6 and thereafter proceeds under the shoe 66 and between the radiation source 11 and the detector 28. The beta rays emanating from the source 54 disposed in the collimating aperture 34 in the roller shaft 31 proceed upwardly through the window 43 formed in the tube tape roller 41 and are intercepted by a mass of tobacco having a square cross-section of dimensions determined by the spacing between the guides 59 and 61 on the one hand and the tubular roller 41 and the window '78 in the detector 28 and of a length determined by the solid angle subtended by the collimating aperture 34 in the roller shaft and collimator 31. The beta rays are attenuated by the mass of tobacco and those which proceed through the tobacco pass through the window 78 in the detector 28 and impinge upon the scintillation crystal 79 to produce light flashes having an intensity and quantity determined by the energy and quantity of the rays reaching the crystal.

The total density of the aluminum windows 43 and 78 disposed between the source 54 and the crystal 79 is chosen with respect to the energy of the source 54 so that an optimal variation in the energy of the beta rays reaching the crystal 79 with respect to variations in density of the tobacco is produced. Referring specifically for the moment to FIGURE 6 of the accompanying drawings, there is illustrated a graph wherein the ordinate is the ratio of the change of energy with respect to the change in density of a material and the abscissa is the initial energy of the emanations impinging upon the material whose density is to be measured. It will be noted that the graph falls sharply at lower energy levels and then levels off and rises slowly to the right as the energy of the emanations increases. It is obvious from this graph that the greatest change in signal intensity or change in intensity of the light produced by the crystal 79 with respect to variations in the density of the tobacco occur at the lower energy or intensity levels of the emanations and therefore it is preferable to work on this portion of the curve. If the energy of the source is initially E1, the density or opacity of the window 43 in the tubular roller 41 and of the window 73 in the end of the source 23 are chosen with respect to the initial energy of the beta rays that in the absence of any tobacco disposed between the windows 43 and 78, the energy is reduced to the energy level E2 along the abscissa of the graph. In consequence, when tobacco passes between the windows 43 and 78 the reduction in energy with variations in thickness follows the portion of the graph at E3 of FIGURE 6 having a larger ordinate. As a result the signal variations produced by the apparatus of the invention with variations in density of the tobacco are maximized and the sensitivity of the instrument is greatly increased over that which would be obtained were the instrument to be operated over a portion of the curve existing to the right of the energy designated by E2.

Returning now to the discussion of the operation of the apparatus of the invention, the emanations from the source 54 proceeding downwardly through the lower portion of the collimating aperture 34 pass through the standard plate 88 so as to provide at the output of the detector 29 a signal representative of the standard weight desired to be produced in the tobacco rod passing between the windows 43 and '78. The signals produced by the detectors 28 and 29 are compared in an electrical circuit to be described subsequently and upon a deviation of the signal generated by the detector 28 from the desired value, as determined by the detector 29 a control function is performed which is intended to restore the density of the tobacco to the desired value. It will be noted that the cross-section of the tobacco being measured is substantially square or rectangular and in consequence relatively little difficulty is experienced as a result of transverse vibrations of the tobacco rod since the vertical height of the rod being measured does not vary with its transverse displacement with respect to the source 54 as is true with a circular rod.

The guides 59 and 61 are fabricated from a material which reflects many incident beta rays at the intensity at which they impinge upon the sides. Specifically, the side guides 59 and 61 may be fabricated from steel and the rays which are directed from the source 54 toward the side guides are reflected therefrom and strike the crystal 79. Not only does this reflective property of the guides 59 and 61 increase the signal level produced by the detector 28 and therefore increase the sensitivity of the apparatus but further the reflection of the beta rays sub stantially increases the portion of the volume of the tobacco investigated or probed by the radio-active emanations. Specifically, beta rays are high speed electrons and therefore constitute discrete particles of matter which proceed through the volume of tobacco in the sensing region. On a geometrical basis it canbe assumed that all portions of this volume are probed by the radio-active emanations, but because of the spherical geometry of the beam, the distinct possibility exists that rays through certain portions or small volumes of tobacco are not detected by the scintillation detector. The multiple reflections of the beta rays from the guides 59 and 61, however, increase the average effective volume probed by the beta rays over that which would be obtained if only those rays which proceed directly through the tobacco were directed to strike the scintillation crystal.

The fact that the two detectors 28 and 29 are displaced by a circumferential length about the roller 11 of approximately two inches, materially reduces the variations and measurements produced by belt wear since it is obvious that the variations in thickness of the belt along a two inch length, should be considerably less than the variations between long lengths of belt such as half the length of the tube belt. Thus, not only does the combination of the detectors 28 and 29 tend to eliminate variations in the measurements due to long term wear of the belt, but it also measures the belt thicknesses over relatively short lengths and eliminates other variations in the belts which would not be detected if large displacements between the measuring areas were permitted. Further, since the two detectors are located quite close to one another, they are subjected to substantially similar environmental conditions such as moisture and temperature and therefore the compensating effect for background error provided by the detector 29 is more nearly accurate than would be possible if the two detectors were located in regions not subjected to the same atmospheric conditions.

Another important feature of the specific arrangement of the source and measuring and compensating detectors is the fact that the two detecting crystals are diametrically opposed and are aligned along the axis of the aperture 34. As a result of this arrangement, the beta rays which are back-scattered from the tobacco subsisting in the region under the crystal 79 proceed downwardly through the aperture 34 and many of them impinge upon the crystal 79 in the detector 29. The quantity of the back-scattered emanations from the tobacco under the crystal '79 which reach the crystal of the detector 29 is a function of the density of the tobacco and therefore those rays which reach the latter crystal add to the measurement produced by the apparatus. The electronic circuitry for comparing the signals produced by the detector 28 with the signals produced by the detector 29, which circuitry will be described in detail later, is such that the signals of the former detector are either negative or positive and those of thelatter detector are of the opposite polarity, so that by directly adding the two signals the difference therebetween is produced. Assume for purposes of example that instead of a beta ray being backscattered, it impinges upon the crystal 79. A negative signal output of detector 28 is increased and the difference between the negative and positive signal is not as great as if the ray were completely absorbed. If on the other hand the beta ray is back-scattered and increases the positive signal of detector 29, then the difference between the negative signal and the positive signal is increased twofold over the difference when the ray is merely completely absorbed, and therefore the rays which are backscattered from the tobacco being measured, and which impinge upon the crystal of the detector 29 add greatly to the sensitivity of the instrument.

A further advantage of the utilization of the detector assembly disclosed is that the crystals '79 and 79' have a considerably greater density than a gaseous detection medium utilized in ionization gauges and therefore the effective volume of the crystal can be considerably less than the effective volume of the gaseous detectors for the same detector efficiency. In consequence of this fact, the length of the cigarette rod measured at any instant is less than that of the other arrangement and control of the apparatus on a less than one cigarette basis is possible. It is apparent that if a detector measures over one or more cigarette lengths, the signal produced by this detector averages the weight of the rod over these lengths and it is not possible to provide control on the basis of less than the length of the detectors.

The desired length of the detector may be calculated in accordance with the present invention by considering the variations in density of the tobacco rod to be sinusoidal variations which behave as travelling waves when viewed at a single location along the rod. The random variations in the density of the tobacco rod can be resolved into their Fourier frequency components and the variations which is a function of distance (x) and time (t); that is, f(x t and investigated at a single frequency such that the time variation is of the form e The latter is the standard formula in which e is the Naperian base number 2.718+; j is the square root of a minus one and w is the frequency in radians and is equal to 21rf where f is the frequency in cycles per second. Thereafter, by a continuous variation of the frequency, there may be generated the frequency response spectrum of the system. Assuming a source of tobacco at a distance x=0, the rod density at a specific point is p=po+p' 16:0; where p is the total density of the rod at the point x=0,

p is the average density of the rod and p is a random variation in density at a specific frequency. At any value of x 0-2) p=po+p' la ns and an amplitude variation which is a function of frequency and detector length. In consequence the variation in weight (Aw) with respect to time is sin 2 l)] which is a function of the form of sin y/y. The plot of the equation which is a plot of change of Weight as a function or" frequency is illustrated as solid line graph of FIGURE 11 of the accompanying drawings.

Two facts must be borne in mind when determining an appropriate length of detector. The first of these facts is that if the detector length is decreased toward Zero in order to increase the frequency response of the system, the amplitude of the signal from the detector approaches zero and relating this to a practical apparatus as the length of the detector decreases, the sensitivity of the detector must rapidly increase. The second fact, which is apparent from the graph of FIGURE 11, is that signals of lower frequency characterized by variations having long time periods, produce large amplitude signals from the detector, but that as the time period decreases, that is, as the frequency of the variation increases, the amplitude of the signal decreases. It will be noted that the solid line graph falls relatively rapidly from a maximum equal to (x -x at the ordinate axis indicating zero frequency of variation toward the abscissa of the graph and reaches a null at a value where the length of the detector is equal to the space period of the variation. Specifically, it can be shown that Equation 4 is equal to zero when at which time x x =(n/2) (v/f) with n=2, 4, 6, 8, etc. It is apparent, therefore, that the length of the detector must lie between these two extremes and must have a length such that the detector response has fallen off only slightly at the maximum frequency of variation, that is, of importance in controlling the cigarette weight. In order to determine the optimum length of the detector, the variation in weight of the rod, as represented by Equation 4, is differentiated with respect to the detector length and the resulting equation is In order to solve Equation 5 for a maximum detector length L the right-hand term of the equation is equated to zero, and it is found that which relates the detector length to a function involving the velocity of the tobacco rod and the maximum frequency to which it is desired to detect. The w term in Equation 6 represents the maximum frequency of variation of density that is of interest and this is designated on the graph of FIGURE 11 by the dotted vertical line labelled w In further explanation of the Equation 6, v is the velocity of the moving rod body, and (o is 21:- tirnes the highest frequency of sinusoidal variation of density, from a pre-established standard in the body. In determining the value of co it is necessary to determine the highest frequency of significance in controlling the average weight of the cigarette. For all practical purposes any sinusoidal variation which has a space period of less than one cigarette is relatively unimportant pro vided the peak of variation is small with respect to the total weight, for instance, is equal to 0.05 times p In order to provide a factor of safety, that is, in order to accommodate those instances in which the variation is not small, a value of 30 cycles per second is chosen which renders the optimum length of the detector equal to one-third a cigarette length or at most a quarter cigarette length in detecting 40 cycles per second at rod velocities of cigarettes per second.

The above derivation may be expressed in non-mathematical terms by considering the graph of FIGURE 11 Which illustrates that as the frequency of the variation increases with a fixed length of detector, the amplitude of the signal produced by the detector decreases slowly at first and then relatively rapidly with respect to equal weight changes. Therefore, the detector length must be chosen such that the response of the detector at the highest frequency of interest has not fallen appreciably so that a given change in Weight at this frequency produces substantially the same signal change as the same change in weight at a lower frequency. By differentiating Equation 4 and solving for maximum and minimum values, the maximum length of the detector is equal to one-half of a cigarette and the minimum length is equal to onethird of a cigarette. With these lengths of detector and a velocity of tobacco rod of 20 cigarettes per second, the system responds to variations in the weight of the rod of between 20 and cycles, respectively, at a signal intensity not appreciably below the maximum signal intensity produced by density variations of lower frequencies.

An additional advantage is obtained in accordance with the present invention by employing a circular detector as opposed to a rectangular detector for measuring the rod (tobacco stream) at a point where it has a greater rectangular cross-section than in the finished rod (tobacco stream). Specifically, as the ratio of the width of the rod (tobacco stream) with respect to the diameter of the circular scintillation crystal approaches one, the detector length is: (a) effectively shortened and (b) the detector length is less discretely defined, that is the dimension corresponding to the longitudinal direction of the rod is not sharply defined. The lack of discreteness of the circular detector eliminates one obvious shortcoming of other types of detectors, since when the detector is nearly rectangular, a sine wave variation having a period equal to the detector length (or integral multiple thereof) cannot be detected as indicated in the solid line graph of FIGURE 11 and for the reasons discussed above. However, when a circular detector having a diameter not appreciably greater than the width of the rod is employed. Equation 4 is modified in such a manner as to produce the dotted line graph of FIGURE 11. It will be noted that the dotted line graph has no complete null and that the variation in signal level with frequency is considerably diminished so that if ca is chosen as 30 c.p.s., the velocity of the rod is 20 cigarettes per second and the detector length is /3 cigarette the response of the detector, over the desired frequency range is substantially uniform amounting to 98% of its maximum response at zero frequency.

Proceeding now to a specific discussion of the control functions performed by the apparatus of the present invention, reference is made to the diagram of FIGURE 7 of the accompanying drawings. To correlate the diagram of FIGURE 7 with the machine drawing of FIGURE 1, the tobacco flow-line or stream is illustrated by the lines 104, 104a, 1116 and 107. Thus, tobacco issues from the main source of hopper 1 and proceeds under the auxiliary hopper 91 which applies a predetermined quantity of tobacco to the cigarette stream and then proceeds through the weight detector and under the hopper 92 which adds a second predetermined portion of the tobacco to the stream. In the diagrammatic showing in FIGURE 7 the weight detector includes the structural part indicated at 28a providing the gap for the tobacco stream having associated therewith the electrical response means indicated at 28 which has been described previously. It may be noted that in the diagrammatic showing of FIG. 7 mechanical elements and connections are shown in broken lines and elements which are essentially electrical are shown in full lines. The total of the tobacco added by each of the sources 1, 91 and 92 represents the final quantity of tobacco which is wrapped into a cigarette rod and thereafter cut into cigarettes. The weight detector 28 produces a signal upon a lead 108 that is fed to a comparison device 1G9 to produce on an electrical lead 111 a signal representative of the difference between the signal on the lead 108 and the signal on the lead 112 generated by the reference and compensation detector 29. The sig nals appearing on the lead 111 are appropriately operated upon by an amplifier and compensator 113 and then coupled via a lead 114 to a further amplifier and compensation network 116 which supplies control signals to a speed control system 117 that controls the position of the motor 26 and therefore of the shaft 21 so as to control the speed of the shaft 22 feeding the hopper 1. The signals appearing on the lead 114 are also coupled via leads 118 and 119 to an amplifier and compensating network 121 and through the network 121 to a short time control apparatus 122 coupled via a connection 123 to control the position of the vane 97 in the first auxiliary mechanism 91. The signal appearing on the lead 114 is further coupled via the lead 118 and a lead 124 to a third amplifier and compensator 126 which provides a control signal to a second short time control apparatus 127 which via the connection 128 controls the position of the vane 97 in the second auxiliary hopper 2 which it will be noted is down stream from the weight detector 28.

The electrical components or units of FIG. 7 are all devices well known to those skilled in the art and are commercially available. For example the amplifiers and compensators 113, 121 and 126 are described in various analog computer textbooks suchas that by Clarence L. Johnson entitled Analog Computer Techniques published by McGraw-Hill, 1956. Reference is made particularly to the circuits shown on pages 59 to 61 of the above textbook. Amplifier 116 is an on-off control amplifier which determines when the speed control 117 turns on and off. When the error signal on line 114 exceeds a predetermined minimum amplifier 116 causes 117 to switch to on and run at a constant run-away speed in the proper direction for a period of time which is proportional to the magnitude of the error on 114. A simple analog computer network computes this on-time and causes amplifier 116 to turn off when the correct speed adjustment has been made. For circuits of this type reference may be had for example to Catalog 4E (March 1958) page 7 of Assembly Products, Inc., Chesterland, Ohio. Short time control 122 is a well known electromagnetic-mechanical torque motor and an energizing balanced power amplifier combination, and short time control 127 is similar except that the delay network 129 is physically integral with the power amplifier. In this latter connection reference is made for a more detailed disclosure to Principles of Automatic Controls by Floyd E. Nixon, page 355, published by Prentice-Hall (1953).

A variation in weight detected by the detector 28 may be a relatively long, an intermediate, or a relatively short variation in the overall density, and therefore weight, of the rod passing between the source 54 and the detector 28. The signal produced on the lead 111, which represents the deviation of the desired weight of the tobacco from the standard as represented by the plate 88, is operated upon by the amplifier and compensating network 113 to eliminate so far as possible high frequency background noise by having a low pass filter characteristic which attenuates those high frequency Fourier components of the signal which have no significant influence with respect to the average weight of a cigarette. That is, signals which indicate small random variations occurring over lengths less than the length of one-quarter cigarette are rendered substantially ineffective. The signal appearing on the lead 114 is operated upon by the compensated amplifier 116 which may operate on the signal in accordance with various predetermined functions. Specifically, the apparatus 116 may include a very low pass filter network and/or other compensating circuits which cause the long time constant closed loop to have optimum control over the average weight of thirty cigarettes consistent with transportation lags of thirty or more cigarettes. In addition an amplifier and compensating network 121 is designed to have optimum control over the average weight /3 to 30 cigarettes consistent with a transportation lag of approximately three cigarettes. Amplifier and compensating network 126 is designed to operate in an open loop control junction to correct for accidental excess variations in lengths of A to three cigarettes within the speed of response limitations of the mechanical auxiliary feed mechanisms.

As previously indicated the control of the hopper 1 may be on the basis of any combination of one of three different controls. The hopper may be basically of a conventional design, and reference is made to FIGURE 12 employing three coacting rollers normally referred to as the main drum 171, the rear drum 172 and the top drum 173 with tobacco being picked by the main drum from a picker roll 174 which deflects tobacco to a Winnower 176 that in turn supplies tobacco to a front steel drum 177. The tobacco on steel drum passes between the drum and a collator plate 178 vibrated by a magnet 179 and the tobacco is removed from the front steel drum 177 by a pin roller 181 and from the pin roller by a picker roll 182. The picker roll 182 deflects the tobacco down through a filler chute 183 onto the hopper tape 2. The hopper will normally include other detail parts mounted in the hopper overhead the operating parts shown adapted to feed the tobacco to the initial roll 172 but such parts are common and well known in the art and are not important for an understanding of the present invention and accordingly are omitted from the drawings in the interests of simplicity. The description of the control means will now be resumed. If the control is applied to the main drum 171 then the control of the machine effected by the channel comprising the elements 116, 117 and 1 is on the basis of one-hundred to one-thousand cigarettes. This means, in effect, that the mechanical inertia of the hopper mechanism and the transportation lag which is determined by the distance from the main drum 171 through the hopper 1 and along the flow path 2 to the source and detector combination is such that the portion of the tobacco stream Whose density has been varied in accordance with a signal produced by the measuring apparatus is not presented to the measuring apparatus until a time has elapsed equal to the transportation time of 100 to 1,000 cigarette lengths therethrough. On the other hand and in accordance with the aforesaid U.S. Patent No. 2,948,281, the control may be applied to the pin roller 181 of the mechanism with the remainder of the system slaved to the speed of the pin roller. In such an arrangement the control of the machine may be effected over twenty-five to one-hundred cigarette lengths, the reduction required to effect the control function resulting from the fact that the pin roller is considerably closer to the detector than the main drum 171 and further that physical inertia involved in the control of the pin roller is less than that of the main drum. Normally, the various rotating parts of the hopper 1 are geared together so that the speed of rotation of all elements are controlled by the speed of a single element. If desired, however, the gear train may be broken and the pin roller and main drum controls may be independent from one another in which case the pin roller may control variations in tobacco density on a twenty-five to one-hundred cigarette basis and the control to the main drum may be effective over variations or a one-hundred to one-thousand cigarette basis.

' It is apparent, of course, that the control channel comprising the control members 116, 117 and hopper 1 must be duplicated in the event that independent controls are applied to the pin roller 181 and the main drum 171, but if the control were applied to the pin roller and the main drum was slaved to the pin roller then the only change in the mechanism illustrated in FIGURE 7 would be in the member 116 wherein signals representing changesover cigarette lengths of twenty-five or more would be passed to the speed control mechanism 117 instead of cutting the signals off at a frequency such that control could be effected only over one-hundred cigarette lengths or more.

As previously indicated, control may be effected over the hopper width so as to detect control of the flow stream on the basis of five cigarette lengths, this being possible since the transportation lag and the difference in inertia of the system would be equivalent of a twenty cigarette length reduction in response. If the control of tobacco applied was effected by controlling the width of the hopper in addition to control of the pin roller and main drum, an additional channel would be provided or if control were applied only to the hopped width, then the characteristic of the circuits of the apparatus 116 would be changed to pass a higher frequency indicative of changes on the basis of five cigarette lengths.

The signals applied to the channel comprising the apparatus 121, 122 and 91 are operated upon by the amplifier and compensator 121 so as to pass those signal frequencies required to effect flow of the source 91 on the basis of three cigarette lengths or more. It can be seen by a reference -to the FIGURE 1, of the accompanying drawings that the hopper 9 1, which may provide from five to fifteen percent of the main stream of tobacco, is located only a relatively short distance from the source and detector combination and since there is substantially no inertia in the auxiliary feed mechanism 91, the only inertia in the system is the apparent inertia due to a transpor-tation lag equivalent to approximately three cigarettes. Again compensating may be included in the apparatus 121 so as to enhance ability of the mechanism to control the weight of the cigarette rod.

The two control channels thus far described are closed loop controls, that is, any correction performed by these channels is detected by the weight detector -28 so that if the correction is incorrect, a further correction is made until the error signal on lead 111 is reduced to an acceptably small quantity. In such a system there is always a danger of instability since if the phase displacement through the closed loop system is greater than onehundred and thirty-five degrees while the open loop gain .is at the same time greater than unity, the feed-back signal will tend to reinforce disturbing influences rather than to eliminate them. In consequence, the loop gain of the control circuits comprising the two channels discussed above, must be less than unity at the high frequencies for which excessive phase shift occurs so that any instability does not exceed acceptable control specifications. Further, in the system described there is al- Ways present a transportation lag between the control apparatus and the detection apparatus. Specifically, and reference is now made to FIGURE 1 of the accompanying drawings, regardless of whether the hopper 1 is controlled or the auxiliary source 91 is controlled or both of these sources are controlled, the controls are displaced upstream from the detector and radioactive source by a finite distance and therefore the effect of a correction applied by either of these tobacco sources cannot be detected until a finite time interval has expired, as determined by the transport velocity of the tobacco stream. Therefore,

a definite limitation is placed upon the open-loop gain of the closed loop systems wherein the control and measurements are physically displaced along a flow path. Theoretically, this open loop gain should be infinite if the error signal is to be zero. Hence it is obvious that for the error signal to be as small as possible, the open loop gain of the closed loop control systems should be as large as possible within the limits of the overall response specifications. Further, since transportation lag has the effect of increasing the phase delay in the open loop which in turn restricts the permissible open loop gain, it is further obvious that decreasing the transportation lag greatly increases accuracy of a closed loop feed-back control system. Thus, in the loop containing tobacco source 91 there is at least an order of magnitude more effective than the loop containing the hopper 1 and pin roller.

In consequence of the remaining limitations upon response to the aforesaid closed loop control, and in accordance with the present invention, the control loop comprising the members 126, 127 and 92 is included in the system to provide an open loop control from which transportation lag may be completely eliminated. Specifically, the control exerted by this loop is eifected by varying the amount of tobacco supplied to the rod by the auxiliary source 92 located downstream from the weight detector. The correction applied by the source 92 may be timed to occur at precisely the instant that the portion of the stream of tobacco whose variation in density produced a signal passes under the source 92. Referring now to FIGURE 1, it is apparent that a finite time interval is required for the tobacco to move from the region of the radio-active source and detector to the region of the auxiliary tobacco source 92. However, since the tobacco passes under the source 92 at a time later than the signal is produced, an appropriate delay may be inserted in the open loop control channel to time the addition of the tobacco to the tobacco rod by the auxiliary source 92 so that the addition can be made in synchronism with the passage of a low density region under the source 92. Therefore, the only limitation in the open loop system of this type so far as times and rates are concerned, is the length of cigarette rod that is measured by the source and detector. Thus, in the present invention since a scintillation crystal is utilized for detecting beta rays, the length of cigarette rod measured by the detection apparatus may be as short as a quarter cigarette length. The correction of variations in the density of tobacco occurring over lengths less than a quarter of a cigarette decreased as discussed above, but all variations occurring over a length greater than twice the length along the flow path of the crystal 79 can be fully detected by the detector and the signals produced thereby may be applied to the auxiliary source 92 so as to provide full compensation therefor. If precise control is desired, a delay correcting network represented by the box 129 may be inserted in the open loop control channel.

It is seen from the above discussion that control provided by the apparatus of the present invention over the weight of cigarettes is extremely flexible and may be effected on a very short time basis and/or a very long time basis and/ or over intermediate time intervals by the apparatus of the present invention. Primarily, the large range of controls may be effected in consequence of the utilization of relatively short length detectors and auxiliary low inertia sources of tobacco which under normal conditions of operation supply to the tobacco stream a predetermined small portion of the quantity of tobacco required. The auxiliary sources 91 and 92 handle relatively small quantities of tobacco and control mechanisms may have relatively low inertia and may be controlled at a far greater rate than the main hopper 1. In addition due to their relatively small sizes, the auxiliary sources may be located at various positions along the tobacco stream without unduly complicating the apparatus. Mounting the relatively small units requires only moderate modification of the machine and then only to the extent necessary to provide adequate support for the auxiliary feed mechanisms. The auxiliary sources 91 and 92 may be completely independent of the main hopper or an endless belt mechanism may be provided for transporting a portion of the winnowed tobacco from the hopper. In the apparatus illustrated in the invention the hoppers 91 and 92 are independent but as indicated immediately above it is not intended to limit the invention to such an arrangement. The apparatus illustrated in FIGURES 1 and 7 constitute equipments utilizing two auxiliary sources of tobacco. It is apparent that either one of the sources may be eliminated or additional auxiliary sources may be provided as required in any specific system.

Referring to FIGURE 8 of the accompanying drawings there is illustrated a schematic wiring diagram of the photomultiplier tube and addition circuits for producing a control signal representing the difference between the signals produced by the two detectors 2S and 29 and a block diagram of the control circuits for the sources 1, 91 and 92. The signal voltages produced by the photomultiplier 82 are coupled across a pair of leads 131 and 132, the latter of which is connected to a source of reference potential, which for the purposes of explanation may be ground. The lead 131 is connected through a coupling capacitor 133 to a junction 134 of reversely poled diodes 136 and 137. The diode 136 is connected to the grounded lead 132 with the anode thereof connected to the junction 134. The diode 137 has its cathode connected to the junction 134 and its anode connected to a junction 13%. The junction 138 is connected to ground through a filter capacitor 139 and is further connected through a resistor 141, constituting a portion of a summation network, to a further junction 142. Proceeding now to the compensation detector 29, the photo-multiplier tube 82 is connected across a pair of leads 143 and 144 with the lead 143 being connected to the same source of reference potential, which may be ground, as the lead 132. The lead 144 is connected through a coupling capacitor 145 to a junction 146 and the junction is connected to the cathode of a diode 147, having a grounded anode. The junction 146 is further connected to the anode of a diode 148 having its cathode connected to a lead 149. The lead 149 is grounded through a filter capacitor 151 and is further connected through a resistor 152 to the junction 142.

In consequence of this circuit arrangement a signal appears at the junction 142 as will become apparent upon a detailed description of the circuit which indicates the difference between the si nals produced by the photomultiplier tubes 82 and 82', the polarity of this signal being determined by which of the two signals is greater.

The signals appearing across the leads 131 and 132 are acted upon by the diodes 136 and 137 such that the positive excursion of the signals appearing at the junction 134 are grounded by the diode 136 and blocked by the diode 137. The negative excursion of signals appearing across the leads 131 and 132 are blocked by the diode 136 and passed by the diode 137 where they are temporarily stored in the filter capacitor 139. Thus, a voltage is applied across the resistor 141 and the load, which is coupled between the junction 142 and ground by means of a connector 153, having a negative polarity and an instantaneous amplitude as determined by the average density of the tobacco being measured by the detector 28. The signals developed by the detector 29 are applied across the leads 143 and 144 and are coupled through the capacitor 144 to the junction 146. The negative excursions of the signals appearing between the junction 146 and the grounded lead 143 are coupled to ground through the diode 147 and are blocked by the diode 148. Positive excursions of the signal are blocked by the diode 147 and coupled through the diode 143 to the capacitor 151.

Thus, a positive signal is developed across the capacitor 151 having an amplitude as determined by the output voltage of the photo-multiplier tube 82'. The voltage across the capacitor 151 is applied via the lead 149 to the resistor 152. The resistors 141 and 152 and the load connected across the coupler 153 constitute a summing network such that the voltage between the junction 142 and the grounded lead 132 is the sum of the negative signal across the capacitor 139 and the positive signal across the capacitor 151. Thus, the actual signal appearing across the terminals of the connector 153 is the difference between the tube signals developed by the photo-multiplier tubes 82 and 82' and therefore constitutes the difference between the actual weight of the cigarette rod being formed and the desired weight for the same rod. The control signal applied across the connector 153 is the signal appearing on the lead 111 of the flow diagram of the FIGURE 7 of the accompanying drawings and constitutes the input signal for the control apparatus.

The fiow diagram of FIGURE 7 has been reproduced in FIGURE 8 and modified to the extent necessary to disclose the actual control system employed. As in FIG- URE 7 the signals appearing on the lead 114 is coupled to the three amplifier and compensating networks 116, 121 and 126. The signal produced by the circuit 116 is applied to a circuit which determines the position of the motor 26 in accordance with the signal amplitude and polarity. The motor 26 controls the position of the shaft 21 in order to vary the output speed of the variable speed of the input drive shaft 22 of the hopper 1.

The output voltages of the networks 121 and 126 are applied to position control circuits 122 and 127, respectively, which through their respective output shafts 156 and 157 control the position of the vanes 97 of sources 91 and 92. Obviously, the solenoid control circuits are employed only if solenoids are employed to control vanes 97. If low inertia motors are employed, then the circuits 122 and 127 would be motor position control circuits.

The photo-multiplier tubes have an advantage over the ionization tube in that they are relatively high gain circuit elements providing for signal gains of the order of magnitude of one to one-hundred million. The utilization of the photo-multiplier tube, therefore, eliminates the necessity for high input resistance amplifying apparatus such as electrometer type of amplifiers which are difficult to maintain or chopper-fed high gain A.C. amplifiers.

A further advantage of the photo-multiplier tube and scintillation crystal combination is its extremely short recovery time compared to a Geiger-Mueller ionization tube. The former can have, by proper design treatment recovery times as fast as six milli-microseconds while the latter usually has a recovery time on the order of two to four hundred microseconds, five orders of magnitude slower. Hence, the latter fails to detect many beta rays that the former will detect. This failure of a Geiger- Mueller tube to detect many beta rays of an intense beam of beta rays represents a many fold decrease in detection efliciency even though its detection efiiciency in the presence of low intensity beta ray beams is on the order of 98%. The photo-multiplier scintillation crystal combination can be designed to operate with the same high efficiency approaching 100% in the presence of a beta ray source of 100 millicuries located one inch from the detector. Of course it is not the intention of this invention to operate the beta ray detector at such a high rate of radioactive disintegration because of the possibility of creating a radiation hazard to operating personnel, but it is important to note that relative high rates can be used so that the low frequency random variation in the number of beta rays occurring in successive short intervals is less than the smallest detectable signal variation. This effect is known to those versed in the art as source noise and it is obvious that the same noise content of any of the above described signals is inversely proportional to the strength of the radioactive source and the maximum number of beta rays that a detector is capable of detecting. Hence it is obvious that the photo-multiplierscintillation crystal combination is vastly superior to the gaseous ionization type of detector.

In the present invention low gain DC. amplifiers hav ng gains of the order of magnitude of ten and/or having chopper draft stabilization may be utilized or an AC. amplifier with synchronous detector following a chopper may also be utilized. In order to stabilize the output of the photo-multiplier tubes against variation in line voltages and other factors which normally produce variations in gains of such tubes, the individual dynodes of the tubes may be regulated as taught in the article, Regulation of the Individual Dynode Voltages for Photo-Multiplier Tubes by O. R. Harris and Bde. Flagge appearing in the IRE Transactions of Nuclear Science at pages 3 to 11 of the March 1957 issue of the Transactions. Additional known techniques may be utilized for stabilizing the electronic circuitry of the apparatus and particularly of the DC. amplifiers if such are employed.

While we have described and illustrated one specific embodiment of our invention, it will be clear that variations of the details of construction which are specifically illustrated and described may be resorted to without departing from the true spirit and scope of the invention as defined in the appended claims.

What We claim is:

1. A radiation source comprising a shaft having an axially-extending aperture, an outer wall, and at least one collimating aperture extending generally perpendicular to the axis thereof and through said wall thereof, a member disposed in the axial aperture of said shaft and having an aperture generally perpendicular to the axis of said shaft, a quantity of radio-active material disposed in said aperture in said member, and a sleeve coaxial with and rotatably mounted on said shaft.

2. The combination according to claim 1, wherein said member is reciprocable in said shaft and comprising means adapted to reciprocate said member into positions such that the aperture therein is in and out of alignment with the collimating aperture in said shaft.

3. The combination according to claim 2, wherein said means for reciprocating said member comprises electromagnetic means for positioning said member such that the aperture therein is in alignment with the collimating aperture, upon energization of said electromagnetic means and spring means for moving said member such that the aperture therein is out of alignment with the collimating aperture upon deenergization of said electromagnetic means.

4. The combination according to claim 1, wherein the collimating aperture in shaft extends completely therethrough and the aperture in said member extends completely therethrough.

5. A machine for forming a mass of material into a rod of substantially uniform density comprising a main source of material, first rate changing means for controlling the rate at which said main source dispenses material, apparatus for forming said material into a rod, a conveyor means for receiving material from said main source and conveying it to said rod forming apparatus, an auxiliary source of material disposed between said main source and said rod forming apparatus and adapted to supply to said conveyor means a relatively small proportion of the material thereon, second rate changing means for controlling the rate at which said auxiliary source dispenses material, means for measuring the variations in density of the material on said conveyor means and for producing a signal indicative of the variations in density from a predetermined desired density, first circuit means for applying signals indicative of relatively slow changes in density to said first rate changing means to vary the rate at which said main source dispenses material, and second circuit means for applying signals indicative of relatively rapid changes in density to said second rate changing means to vary the rate at which said auxiliary source dispenses material.

6. The combination according to claim 5, wherein said first rate changing means comprises means for varying the width of said main source along said conveyor means on the downstream side thereof.

7. The combination according to claim 5, wherein said conveyor means includes a roller and wherein said means for measuring includes a source of radio-active material and means for mounting said source of radio-active material in said roller.

8. The combination according to claim 7, wherein said means for measuring further includes two radiation detectors disposed on diametrically opposed sides of said roller with one of said radiation detectors disposed on an opposite side of the material on said conveying means from said roller.

9. A cigarette-making machine comprising a tobacco conveying means, a main hopper for showering tobacco onto said conveying means, control apparatus for controlling the rate at which said main hopper showers tobacco on said conveying means, a cylindrical cigarette rod forming apparatus disposed to receive tobacco from said conveying means, a shoe means disposed between said main hopper and said rod forming apparatus for compressing the tobacco on said conveying means, said conveying means having a roller and an endless belt disposed above and below said roller, radio-active source and detector means for producing a signal in accordance with variations in the density of the tobacco on said conveying means from a desired density, said source and detector means including a source of radio-activity, means for mounting said source in said roller, said source and detector means further including a detector of radio-activity, means for mounting said detector above a portion of said belt having tobacco thereon and circuit means for applying the said signal developed by said source and detector means to said control means so as to vary the rate at which said main hopper supplies tobacco in such a sense as to reduce said signal.

10. The combination according to claim 9, wherein said roller is disposed below said shoe and wherein said means for mounting said detector includes said shoe.

11. The combination according to claim 9, wherein said source and detector means includes a standardization and compensation detector and means for mounting said standardization and compensation detector in a position below the portion of said endless belt disposed below said roller.

12. The combination according to claim 9, wherein said roller comprises a shaft having an axially-extending aperture, and at least one collimating aperture extending generally perpendicular to the axis thereof, and through a wall thereof, a member disposed in the axial aperture of said shaft and having an aperture generally perpendicular to the axis of said shaft means for mounting said source in' the aperture in said member and a shoe coaxial with and rotatably mounted on said shaft.

13. The combination according to claim 12, wherein said member is reciprocatable in said shaft and comprising means adapted to reciprocate said member into positions such that the aperture therein is in and out of alignment with the collimating aperture in said shaft.

14. The combination according to claim 12, wherein said means for reciprocating said member comprises electromagnetic means for positioning said member such that the aperture therein is in alignment with the collimating aperture, upon energization thereof and spring means for moving said member such that the aperture therein is out of alignment with the collimating aperture upon deenergization of said electromagnetic means.

15. The combination according to claim 12, wherein the collimating aperture in shaft extends completely therethrough and the aperture in said member extends completely therethrough.

16. The combination according to claim 15, wherein said detector is aligned with said collimating aperture in said shaft.

17. The combination according to claim 16, wherein said source and detector means includes a standardization and compensation detector and means for mounting said standardization and compensation detector in a position below the portion of said endless belt disposed below said roller.

18. The combination according to claim 17, wherein said roller is disposed below said shoe and wherein said means for mounting said first-mentioned detector includes said shoe.

19. The combination according to claim 9, wherein said detector has a maximum length L in the direction of movement of said material in accordance with the formula Where v is the velocity of the material and w is directly proportional to the maximum rate of density variation of interest.

20. The combination according to claim 19, wherein said detector is a circular disc of scintillation material and wherein the compacted tobacco defined by said shoe has a width at least of the same order of magnitude as the diameter as said disc.

21. The combination according to claim 9, wherein said source is a source of beta-rays and wherein said shoe comprises a pair of side walls disposed adjacent opposite sides of said belt and a top wall, said shoe being fabricated from a material which reflects beta-rays.

22. The combination according to claim 9, wherein said control means includes deflector means for varying the width of the hopper on the downstream side thereof.

23. The combination according to claim 22, wherein said main hopper includes a plurality of rotating elements and wherein said control means further includes speed changing means for varying the speed of rotation of said rotating elements.

24. The combination according to claim 9, wherein said main hopper includes a plurality of rotating elements and wherein said control means further includes speed changing means for varying the speed of rotation of said rotating elements.

25. The combination according to claim 23, wherein said circuit means includes further circuit means for applying signals indicative of a relatively slow variation in density of tobacco to said speed changing means and for applying signals indicative of moderate rates of variation of density of tobacco to said deflector means.

26. The combination according to claim 9, further comprising at least one auxiliary source of tobacco disposed between said main hopper and said rod forming V apparatus and adapted to shower tobacco on said conveying means, further control means for varying the rate at which said auxiliary source feeds tobacco and circuit means for applying said signals to said further control means to effect variation of the rate of feed therefrom in such a sense as to reduce said signal.

27. The combination according to claim 26, wherein said auxiliary source is disposed upstream from said source and detector means.

28. The combination according to claim 26, wherein said auxiliary source is disposed downstream from said source and detector means.

29. The combination according to claim 26, further comprising at least two said auxiliary sources, one of said auxiliary sources disposed upstream from said source and detector means and the other of said auxiliary sources disposed downstream from said source and detector means.

30. The combination according to claim 24, further comprising at least one auxiliary source of tobacco dis posed between said main hopper and said rod forming 29 apparatus and adapted to shower tobacco on said conveying means, further control means for varying the rate at which said auxiliary source feeds tobacco and circuit means for applying said signals to said further control means to effect variation of the rate of feed therefrom in such a sense as to reduce said signal.

31. The combination according to claim 30, wherein said auxiliary source is disposed upstream from said source and detector means.

32. The combination according to claim 30, wherein said auxiliary source is disposed downstream from said source and detector means.

33. The combination according to claim 30, further comprising at least two said auxiliary sources, one of said auxiliary sources disposed upstream from said source and detector means and the other of said auxiliary sources disposed downstream from said source and detector means.

34. The combination according to claim 23, further comprising at least one auxiliary source of tobacco disposed between said main hopper and said rod forming apparatus and adapted to shower tobacco on said conveying means further control means for varying the rate at which said auxiliary source feeds tobacco and circuit means for applying said signals to said further control means to effect variation of the rate of feed therefrom in such a sense as to reduce said signal.

35. The combination according to claim 22, further comprising at least one auxiliary source of tobacco disposed between said main hopper and said rod forming apparatus and adapted to shower tobacco on said conveying means, further control means for varying the rate at which said auxiliary source feeds tobacco and circuit means for applying said signals to said further control means to effect variation of the rate of feed therefrom in such a sense as to reduce said signal.

36. In an apparatus having means for moving longitudinally an elongated body, a radiation detector for detecting variations in density of the moving body comprising a detector element having a maximum length (L) in the direction of movement of said body in accordance with the formula Z h where v is the velocity of the moving body and ca is 21:- times the highest permissible frequency of sinusoidal variation of density, from a pre-established standard, in said body.

37. In a continuous rod cigarette making machine, the combination comprising a moving conveyor, a series of tobacco feeding stages sequentially arranged adjacent said conveyor and adapted to feed tobacco thereto to form a composite stream of tobacco, a detector disposed between at least two of said stages for detecting variations in the density of the tobacco in said moving stream,

said detector having output signals representative of said variations, said feeding means including first and second hoppers for showering tobacco onto said conveyor, said first hopper having first regulating means for varying the tobacco shower therefrom in accordance with longterm variations in the density of said tobacco stream, said second hopper having second regulating means for rapidly varying the tobacco shower therefrom in accordance with short-term variations in the density of predetermined increments of said tobacco stream, means serially interposed between said detector and said first regulating means for averaging said signals to cause said regulating means to correct for said long-term variations, and means connected between said detector and said second feed regulating means operable to cause said second regulating means to correct for short-term variations in the density of successively detected increments of said stream.

38. In a system for controlling the relative density of individual cigarettes produced by a cigarette making machine of the continuous rod type, the combination comprising, a conveyor, a main tobacco feed for feeding tobacco to said conveyor, said main feed having regulating means for varying the rate of tobacco being fed, a subsidiary feed disposed adjacent said conveyor for showering tobacco thereon to form a composite stream of tobacco, first detecting means interposed between said main and subsidiary feeds for detecting short-term variations in the density of successive increments of said tobacco supplied by said main feed, means associated with said first detecting means and operative in response to said short-term variations for varying the rate of tobacco showered by said subsidary feed to compensate for said variations in the density of said tobacco stream delivered by said main feed, second detecting means operative to detect long-term variations in the density of said composite stream, and means connected to said second detecting means and said main feed regulating means and operative to cause said main feed regulating means to correct for said detected long-term variations in said composite stream.

39. In a mechanism for detecting variations in density of a moving body, a source of radiation and a radiation detector element, said element comprising a generally circular disc of scintillation material having a diameter in a plane parallel to the direction of movement of the body as large at least as the width of the body perpendicular to the direction of movement of the body.

References Cited in the file of this patent UNITED STATES PATENTS 2,512,247 Fua et a1 June 20, 1950 2,704,079 Molins Mar. 15, 1955 2,737,186 Molins et a1. Mar. 6, 1956 

9. A CIGARETTE-MAKING MACHINE COMPRISING A TOBACCO CONVEYING MEANS, A MAIN HOPPER FOR SHOWERING TOBACCO ONTO SAID CONVEYING MEANS, CONTROL APPARATUS FOR CONTROLLING THE RATE AT WHICH SAID MAIN HOPPER SHOWERS TOBACCO ON SAID CONVEYING MEANS, A CYLINDRICAL CIGARETTE ROD FORMING APPARATUS DISPOSED TO RECEIVE TOBACCO FROM SAID CONVEYING MEANS, A SHOE MEANS DISPOSED BETWEEN SAID MAIN HOPPER AND SAID ROD FORMING APPARATUS FOR COMPRESSING THE TOBACCO ON SAID CONVEYING MEANS, SAID CONVEYING MEANS HAVING A ROLLER AND AN ENDLESS BELT DISPOSED ABOVE AND BELOW SAID ROLLER, RADIO-ACTIVE SOURCE AND DETECTOR MEANS FOR PRODUCING A SIGNAL IN ACCORDANCE WITH VARIATIONS IN THE DENSITY OF THE TOBACCO ON SAID CONVEYING MEANS FROM A DESIRED DENSITY, SAID SOURCE AND DETECTOR MEANS INCLUDING A SOURCE OF RADIO-ACTIVITY, MEANS FOR MOUNTING SAID SOURCE IN SAID ROLLER, SAID SOURCE AND DETECTOR MEANS FURTHER INCLUDING A DETECTOR OF RADIO-ACTIVITY, MEANS FOR MOUNTING SAID DETECTOR ABOVE A PORTION OF SAID BELT HAVING TOBACCO THEREON AND CIRCUIT MEANS FOR APPLYING THE SAID SIGNAL DEVELOPED BY SAID SOURCE AND DETECTOR MEANS TO SAID CONTROL MEANS SO AS TO VARY THE RATE AT WHICH SAID MAIN HOPPER SUPPLIES TOBACCO IN SUCH A SENSE AS TO REDUCE SAID SIGNAL. 